1. Field of the Invention
This invention relates to a water-based ink used chiefly in ink-jet recording, an ink tank having the ink, and an ink-jet recording process.
2. Related Background Art
Hitherto, changes in tone of recorded images are taken up as a technical subject in the field of ink-jet recording. As the changes in tone of images, it may be mentioned that images recorded on recording mediums undergo discoloration due to light, the air and so forth. Besides inks stored in ink tanks over a certain period of time undergo deterioration with time and images recorded using such inks undergo changes in tone compared with images recorded using unstored fresh inks. The cause of the changes in tone of images recorded using inks stored over a certain period of time is also chiefly the deterioration of coloring materials.
As a main measure against this subject, it may be mentioned that a different coloring material which relatively can not easily deteriorate is additionally incorporated so that, even when an original coloring material has deteriorated, the changes in tone of images can consequently be restrained by the effect the coloring material incorporated additionally has.
Meanwhile, the reliability of inks has also been a technical subject for a long time, as exemplified by the deposition of coloring materials at nozzles of recording heads.
As a measure against this subject, it is proposed to incorporate in an ink a monomethyl ether compound of propylene oxide (e.g., Japanese Patent No. 2522325).
However, incorporation of many kinds of coloring materials in an ink in order to restrain the changes in tone of images may lead to a rise in cost. Also, depending on the tone of a coloring material additionally incorporated, initial-stage images may have an undesirable tone. Moreover, since individual coloring materials have different characteristics, a solvent, additives and so forth must further be added in order to restrain a difficulty that other ink performance, in particular, ink reliability may come poor. This may make ink formulation complicate. In ink tanks holding inks of this type, it has been difficult to improve storage stability.